In a procedure for production of a PDP, various heat treatments are applied to a glass substrate. Accordingly, a glass substrate for a PDP is required to have a high glass transition temperature to such an extent that no thermal deformation nor thermal shrinkage occurs by the heat treatment, and have a thermal expansion coefficient close to that of soda lime glass. Further, a PDP becomes large in recent years, and accordingly a glass substrate having a low specific gravity has been required.
As a glass substrate to achieve such objects, for example a glass substrate as disclosed in Patent Document 1 may be mentioned.
Further, in addition to the above objects, a glass substrate for a PDP is required not to undergo yellowing. The yellowing is a phenomenon such that the surface of a glass substrate is discolored to be yellow when silver electrodes for generating plasma discharge are formed by firing on the surface of the glass substrate.
To solve the above yellowing, there are known, for example, a flat panel display substrate (e.g. Patent Document 2) wherein a surface on which metal electrodes are to be formed is polished to remove a reducing foreign layer formed on the surface, a plasma display device (e.g. Patent Document 3) wherein the amount of Fe2O3 is less than 2,000 ppm (0.2%) and metal electrodes are made of silver, and a process for producing a glass substrate for an image display device (e.g. Patent Document 4) wherein control is made to reduce the reduction power in a float bath when the amount of Sn2+ in the glass substrate exceeds a tolerance.